1. Field of the Invention:
The present invention relates to a polishing apparatus, and more particularly to a polishing apparatus for polishing a surface of an object to be polished (a substrate) such as a wafer.
2. Description of the Related Art:
A chemical mechanical polishing (CMP) is a technology for polishing a surface of a wafer by a chemical action of a polishing liquid and a mechanical action of abrasive particles contained in the polishing liquid. Generally, a polishing apparatus for carrying out the “CMP” includes a polishing table for holding a polishing pad, a polishing head for pressing the wafer against the polishing pad, and a polishing liquid supply mechanism for supplying the polishing liquid (e.g., slurry) to the polishing pad. The polishing head includes a top ring for holding the wafer and pressing the wafer against a polishing surface of the polishing pad, and a top-ring operating mechanism for operating this top ring.
The wafer is pressed against the polishing surface of the polishing pad by the top ring, and the polishing table and the top ring are rotated in this state. The wafer is brought in sliding contact with the polishing surface of the polishing pad in the presence of the polishing liquid, so that the surface of the wafer is polished. After polishing of the wafer is terminated, an atomized fluid is supplied toward the polishing surface of the polishing pad from an atomizer to clean the polishing surface, as disclosed in Japanese laid-open patent publication No. 2008-296293.
When the surface of the substrate such as a wafer is polished while supplying the polishing liquid, the polishing liquid adheres to the polishing head including the top ring. The polishing liquid remaining on the polishing surface adheres to the polishing head also at the time of cleaning the polishing surface by the atomizer. The polishing liquid which has adhered to the polishing head is gradually dried, and may fall onto the polishing surface eventually. Such dried polishing liquid causes scratches on the surface, being polished, of the substrate.